Early rise in central venous pressure during a spontaneous breathing trial: A promising test to identify patients at high risk of weaning failure?

Background The spontaneous breathing trial (SBT) assesses the risk of weaning failure by evaluating some physiological responses to the massive venous return increase imposed by discontinuing positive pressure ventilation. This trial can be very demanding for some critically ill patients, inducing excessive physical and cardiovascular stress, including muscle fatigue, heart ischemia and eventually cardiac dysfunction. Extubation failure with emergency reintubation is a serious adverse consequence of a failed weaning process. Some data suggest that as many as 50% of patients that fail weaning do so because of cardiac dysfunction. Unfortunately, monitoring cardiovascular function at the time of the SBT is complex. The aim of our study was to explore if central venous pressure (CVP) changes were related to weaning failure after starting an SBT. We hypothesized that an early rise on CVP could signal a cardiac failure when handling a massive increase on venous return following a discontinuation of positive pressure ventilation. This CVP rise could identify a subset of patients at high risk for extubation failure. Methods Two-hundred and four mechanically ventilated patients in whom an SBT wa

Relationship of systemic, hepatosplanchnic, and microcirculatory perfusion parameters with 6-hour lactate clearance in hyperdynamic septic shock patients: an acute, clinical-physiological, pilot study

Background: Recent clinical studies have confirmed the strong prognostic value of persistent hyperlactatemia and delayed lactate clearance in septic shock. Several potential hypoxic and nonhypoxic mechanisms have been associated with persistent hyperlactatemia, but the relative contribution of these factors has not been specifically addressed in comprehensive clinical physiological studies. Our goal was to determine potential hemodynamic and perfusion-related parameters associated with 6-hour lactate clearance in a cohort of hyperdynamic, hyperlactatemic, septic shock patients. Methods: We conducted an acute clinical physiological pilot study that included 15 hyperdynamic, septic shock patients undergoing aggressive early resuscitation. Several hemodynamic and perfusion-related parameters were measured immediately after preload optimization and 6 hours thereafter, with 6-hour lactate clearance as the main outcome criterion. Evaluated parameters included cardiac index, mixed venous oxygen saturation, capillary refill time and central-to-peripheral temperature difference, thenar tissue oxygen saturation (StO(2)) and its recovery slope after a vascular occlusion test, sublingual microcirculatory assessment, gastric tonometry (pCO(2) gap), and plasma disappearance rate of indocyanine green (ICG-PDR). Statistical analysis included Wilcoxon and Mann-Whitney tests. Results: Five patients presented a 6-hour lactate clearance = 10%, they presented a worse hepatosplanchnic perfusion as represented by significantly more severe derangements of ICG-PDR (9.7 (8-19) vs. 19.6 (9-32)%/min, p <0.05) and pCO(2) gap (33 (9.1-62) vs. 7.7 (3-58) mmHg, p <0.05) at 6 hours. No other systemic, hemodynamic, metabolic, peripheral, or microcirculatory parameters differentiated these subgroups. We also found a significant correlation between ICG-PDR and pCO(2) gap (p = 0.02). Conclusions: Impaired 6-hour lactate clearance could be associated with hepatosplanchnic hypoperfusion in some hyperdynamic septic shock patients. Improvement of systemic, metabolic, and peripheral perfusion parameters does not rule out the persistence of hepatosplanchnic hypoperfusion in this setting. Severe microcirculatory abnormalities can be detected in hyperdynamic septic shock patients, but their role on lactate clearance is unclear. ICG-PDR may be a useful tool to evaluate hepatosplanchnic perfusion in septic shock patients with persistent hyperlactatemi